1. Field of the Invention
The present invention relates to a structure for effectively discharging heat, generated by electronic devices, from or out of an electronic apparatus housing on or within which the former are mounted, such as a telecommunication apparatus housing. Particularly, the present invention is suitably applied to thin and small sized electronic apparatuses of a type typified by a single main printed circuit board.
2. Description of the Related Arts
Electronic apparatuses have become small-sized in accordance with the development of LSI technology. Accompanied therewith, the removal of heat, generated by such densified electronic devices, out of a system (or housing) within which they are installed has been a serious problem. Particularly, in small-sized apparatuses with a volume of less than 1 l, and since there is no space for providing a fan to forcibly cool the electronic devices, it is necessary to adopt a natural cooling system.
As shown in FIG. 8(a) and 8(b), the conventional cooling structure comprises a fin plate 23 common to plural electronic devices 22, such as plural LSI devices, mounted on a printed circuit board 21. The fin plate 23 is positioned so as to be in contact with the respective heat-conductive surfaces of the electronic devices 22 and fixed on the printed circuit board 21 by means of screws 26. Upper and lower springs 24, 25 are arranged around the respective upper and lower halves of each corresponding screw 26 so that close contact between the fin plate 23 and the electronic devices 22 is enhanced, while protecting the latter from the weight of the former. Reference numerals 27, 28 designate, respectively, a housing and a ventilation opening.
The above prior art cooling structure has the following drawbacks:
1) A connection area between the printed circuit board and the electronic devices mounted thereon is liable to be damaged by vertical vibration caused by the heavy fin plate supported in a floating manner above the printed circuit board by the springs.
2) It is very difficult to bring all electronic devices, such as LSI devices, into close and uniform contact with the common fin plate, because said electronic devices have inherent manufacturing dimensional errors (i.e., variations) in the outer dimensions thereof, to which variations of the thickness of solder in the connection area is further added. This tendency of having dimensional variations is particularly pronounced when the printed circuit board has a curvature and is under torsion. Of course, this prior art cooling structure system cannot be adopted if any of the electronic devices to be mounted on the printed circuit board has a height different from the others.
3) The problems cited in item 2) can be solved by providing a separate and respective, individual fin plate on each of the plural electronic devices, but this results in a considerable reduction of the mounting efficiency of same.
4) The number of parts increases, resulting in higher manufacturing costs.